In order to improve corrosion resistance of a substrate made of aluminum or an aluminum alloy (hereinafter also referred to as “an aluminum substrate”), the surface of an aluminum substrate is conventionally subjected to chemical conversion treatment to form a covering film by a chromium chemical conversion treatment agent such as a chromate.
However, from the viewpoint of safety of chromium, it is desirable to carry out chemical conversion treatment by a chemical conversion treatment agent containing no chromium (i.e. non-chromium chemical conversion treatment). Patent Document 1 discloses a non-chromium chemical conversion treatment agent containing zirconium, titanium or vanadium and containing no chromium.
Patent Document 2 discloses an aluminum substrate containing a powder coating material comprising a fluorinated resin, a polyester resin, a pigment and specific core-shell acrylic resin particles and a coating film formed from the powder coating material.